Electronic system to control cooling of molds in glassware forming machines

ABSTRACT

An electronic system to control the cooling of molds in glassware forming machines, wherein the articles and/or the molds in which said articles are being produced, are subjected to a suitable cooling to control the thermal relation therebetween so that the articles can be suitable handled and shaped. In this system, the velocity of the machine, the heat profile of the glass gobs and the gob weight are continuously detected and fed as signals to a microprocessor which determines the heat exitation of the molds when receiving the glass gobs, in order to control the necessary cooling air flow rate and compensate for variations in the thermal conditions of the molds. Said microprocessor is also fed, at predetermined intervals of time, with signals representative of the pressure, temperature and humidity of the cooling air, in order to determine the physical properties of the cooling air and relate them with the operation conditions of the machine for compensating for changes in the physical conditions of the ambient, and for forecasting the changes in the ambient conditions for correcting, if necessary, the parameters initially gave to said microprocessor up-dating and self-correcting those initial values and for maintaining the operation of the cooling system even when said pressure, temperature and humidity signals are lost.

This application is a continuation of application Ser. No. 543,110 filedon Oct. 18, 1983, now abandoned.

BACKGROUND OF THE INVENTION

In shaping glass articles, molten glass gobs are fed to the individualshaping sections of the machines. The gobs are received in molds inwhich, either a parison is first formed by the press-and-blow orblow-and-blow process and then the final article is shaped by blowing,or else, the article is shaped directly in the molds.

The molds continuously receive gobs of molten glass and graduallyincrease in temperature. It is known that between the molds and thearticles that are being shaped there is a heat compromise in that themolds must be kept at a temperature making it possible to maintain aheat balance between the glass and the mold. The molds must not be sohot that it additionally heats the glass to such a degree that therequired stiffness for handle the articles cannot be achieved. On theother hand, the mold must not be so cold that it cools the glass andsolidifies it more than necessary, impeding the suitable shaping of thearticle.

Heat control of the process of shaping glass and particularly glassbottles is very complex due to the number of variables including cycletime, mold temperature, weight of the articles and air temperature,which must be within certain limits to maintain good and uniform qualityof the final product. Many decades of experience in the shaping processhave established limits for each of the many variables. Each differentarticle requires a different set of operating parameters which are basedon prior experience in producing the articles and if an entirely newarticle is involved, operating parameters are established from priorexperience with a similar article. This, together with high productiondemands, fluctuations in the cooling fluid temperature and the variousdesignes of the shaping machines, cause the requirements for extractionof heat from the molds to vary widely. The molds are cooled, for themost part, by forced air which even though air has a low heat capacityand is not an ideal medium for heat transfer, it is however, moreeconomical and easy to use in comparison with other cooling systems.

It is common practice in multisection machines to provide a singlecooling air supply which is divided among the various sections of themachine and control of the total flow compensates for variations thatoccur in practice. It is important to compensate for these variations,since if they are not taken into consideration, the amount of coolingexperienced by each particular mold changes, which leads to insufficientor excessive cooling and improperly formed glass articles that have tobe thrown away. Two main sources of variation in the mold cooling systemwill be considered here.

A source over which it is not possible to exert effective control is theambient air surrounding the machine because both the air temperature andits humidity change daily and seasonally. The other source comprises thecondition of the cooling system such as the temperature and pressure ofthe cooling air supply, the properties of the cooling fluid such ashumidity, viscosity, specific heat, conductivity, density, etc., andalmost all the operating parameters of the machine, including type ofglass handled, glass temperature, weight of glass gobs from which thearticles are produced, temperature of the molds, operating time (cutsper minute), type of machine, etc.

Another important change in the cooling conditions under which themachine operates occurs from disturbances in the cooling air supply tothe machine and/or when operating all or less than all the individualsections in a multisection machine.

Controlled cooling of molds in machines which produce glass articles,was originally done manually and was totally dependent on the judgmentand experience of the operator. There was no analysis of causes andeffects, and the results were far from optimal. Manual control resultedin a relatively high loss of articles and correspondingly a considerablereduction of production, because only when the operator realized thatthe articles did not have suitable characteristics, did he makeadjustments which in his experience he considered suitable. There wouldbe a preliminary loss of articles and after manual adjustments had beenmade and a period passed for the system to reach its heat balance, therewould be a secondary loss of articles. Finally, when a more or lesssuitable heat balance was obtained, other disturbances occurred fordifferent causes, such as variation of the furnace temperature thatcaused the glass to be too cool or too hot, a slight variation in theweight of the gob, and in general, internal and/or external heat changes(climatological changes) that required new adjustments. Thus, there wasa third loss of articles until a state of equilibrium was attained.Continuous monitoring of the cooling by the operator with a considerablesacrifice in production were required which increased the manufacturingcosts of the glass articles.

U.S. Pat. No. 3,860,407 of Fertik, issued on Jan. 14, 1975, describes asystem for controlling the cooling of the molds in a glass formingmachine which involves compensating the pressure set point for thecontrol of the cooling air to correct for changes in the temperature ofthe cooling air and changes in the mass flow rate of the glass. In saidsystem, the actual pressure and temperature of the cooling air arecontinuously compared with predetermined pressure and temperature setpoints for an established cooling process in order to compensate forvariations from said predetermined set points.

The main problem with said system is that it is blind about the actualthermal exitation of the molds. In said system the pressure andtemperature of the cooling air in the duct are continuously monitoredbut it does not take into account the actual physical conditions of thecooling air (depending of the physical conditions of the environment)which are of substantial influence in the thermal excitation of themolds. On the other hand, said system discloses that block 76 is afunction of the speed of the machine and that the position of tab 86 ais proportional to weight of the glass gobs, but these data serve onlyto be compared with those of the predetermined set points in order tocompensate for deviations from said set points. Concluding, the mainproblem of said system arises when the conditions of the cooling processcould be at the desired set points, but the actual needs of said coolingprocess could be entirely different from said conditions established bythe set points.

U.S. Pat. No. 3,953,188 of Fertik also, issued on Apr. 27, 1976, includesome improvements over the above cited patent in that during conditionsof maximum and minimum flow of the cooling air, the balance of heattransfer between the air and the parisons in modified by modifying theset points of the temperature controllers of the feeder or alternativelyby changing the speed of the machine.

As in the previous mentioned system, in the above system the coolingprocess depends on the comparation of the actual conditions of pressureand temperature of the cooling air with those provided as set points,but including security means for saturation conditions.

U.S. Pat. No. 4,104,046 of McCreery, issued on Aug. 1, 1978, describes asystem of automatic temperature control applied to a machine forcontinuous shaping of glass articles of the press-and-blow type. Theconditions of heat transfer in the parison shaping units areautomatically detected and the supply of cooling air, to these units isautomatically controlled, to maintain uniform quality in the finalshaped articles. In said system, the fluid passages are provided to makethe cooling air circulate to the parison mold and the piston of eachshaping unit and this air supply is controlled automatically in keepingwith the heat transfer of these members. The control is automated bytemperature detection instruments, such as infrared cameras placed inselected positions in the path of travel of the parison mold and pistonof each of the shaping units of the machines. The cameras produce asignal from each member, which operates a control that, in turn,operates a pressure load regulator, such as an electropneumatictransducer in the cooling air supply line for that particular member. Inthis way, controlled temperature conditions are maintained to produceuniform articles, by avoiding excessive heating or cooling of theparison molds.

In said system the pressure of the cooling air is regulated depending onthe temperature of the molds, but it does not take directly into accountthe actual exitation of the molds which depends also on the weight ofthe glass gobs and the velocity of the machine which determines thenumber of glass gobs processed by the molds. Furthermore it does nottake directly into account the physical properties of the cooling airwhich are of substantial influence in the thermal excitation of themolds.

Further problems arise in said system because of the gases of oil andgrease and the oxides appearing in the molds, all of which affect themeasurements of the temperature of the mold cavities by the cameras.

U.K. Patent application GB No. 2011128 A, filed Dec. 1, 1978 andpublished July 4, 1979, describes a cooling control system to controlthe cooling of various parts of an independent section of a machine forshaping glass articles. The cooling air which goes through a coolingduct is controlled by measuring the cooling capacity of the airdetermined by placing a body whose material and surface characteristicsapproximate those of the molds in the air flow and measuring its surfacetemperature and simultaneously measuring the pressure of the cooling airsupply. The flow of the air through the duct is increased or reduced tokeep the pressure in the duct at a set point which depends on thetemperature measured on the surface of the body located in the coolingair current.

That system also presents the same problem of the temperature set pointestablished by the mold simmulator body.

As can be seen from the above disclosure, practically all of saidsystems are based on a constant thermal excitation applyed to certainfixed temperature conditions.

With this background, the present invention, trough an analysis of therequirements of the process for making bottles, defines the needs of:

1. Determining the actual thermal excitation of the molds in order to,through a predetermined model, if a variation on the thermal conditionof entrance to the mold appear, the cooling system could compensate thecooling needs for said variations.

Applying the time series methodology on valuating the thermal excitationproduced by the glass gobs to the molds, the time of response of themolds was determined. On this basis, if an indication of the velocity ofthe machine (through a gob cutting sensor) is obtained and if thethermal profile of the glass gobs (measured through a gob sensor placedat the output of the delivery equipment and at consecutive sampling) aswell as the weight of the glass gobs (by weighing the finished articlesor by some other signal available from the machine) are known, it ispossible to accurate know the thermal excitation of the molds byadaptative control mathematic models.

2. Making the process of cooling the molds independent of the ambientvariations by monitoring, at predetermined intervals of time, saidambient variations and conditions of the manufacturing process, fordetermining the physical properties of the cooling air and its coolingcapacity for said manufacturing process conditions in order tocompensate for said ambient variations.

To achieve the above it is first necessary to define a heat model inwhich the variation both of the ambient medium and the manufacturingprocess conditions would be related so that an automatic control couldbe performed that would have the enormous advantage of beingsufficiently versatile, that the cooling process would be independent ofthe ambient conditions and manufacturing process.

As it is well known in tha art, theoretical research associated with theheat transfer mechanism by forced convection in cooling of molds in verycomplicated and so far it has not been possible to calculate a heattransfer coefficient by analytic methods.

However, the inventors here discovered that by applying the technique ofdimensional analysis, the variables involved in the process of heattransfer by forced convection can be grounded in nondimensional terms tobe able to find the heat transfer coefficient as a function of theseterms, and by making a stable state energy balance, a heat model isobtained as a function of variables that are easy to measure andinterpret.

In this way, with the method of dimensional analysis it was possible toestablish an equation for the coefficient of heat transfer by forcedconvection, as a function of the variables involved in the process, andfrom the stable state energy balance, it was concluded that the moldsand their parts acquire a temporary heat energy storage and that duringthe entire operation cycle they act solely as a transfer mechanism.

Thus, with te equation of the heat transfer coefficient and the energybalance equation, a heat model was reached whereby through a simplemeasuring system, operational parameters of the mold cooling systemcould be established.

The representative equation of the heat model discovered by theinventors of this invention is the following:

    nlog P=(log β*-jm)-(1+jα) log.(ts-Ta)

where:

β*--is a factor that is a function of the conditions of operation andgeometry of the machines (type of glass, amber, georgia green, etc.,glass temperature, weight of article, type of mold, cycle time, geometryof nozzles, type of machine, blow pressure, no. of sections,lubricating, physical state of mold, etc.);

m--is a factor that is a function of the physical conditions of thecooling fluid (viscosity, density, temperature, humidity, etc.);

n--is a factor that relates the air velocity with the static pressure(turbulence, nozzle losses, leaks, etc.);

j--is a factor that is a function of the distribution of speed of thecooling fluid over the mold;

p--is the static pressure of the cooling fluid;

ts--is the temperature of the mold wall;

Ta--is the temperature of the ambient air.

This equation describes the process of cooling of molds by forcedconvection and expresses what the best way will be to achieve anefficient cooling of the molds since it involves in the first place theproperties of air as the cooling fluid in its coefficients m and α.

To obtain coefficients α and m, it is known that the cooling capacity ofthe cooling fluid (air) depends on its density ρ and its viscosity μ,but, these are a function of the temperature and relative humidity ofthe air, at a particular atmospheric pressure. We can therefore, graphon a logarithmic scale ρ/μ against a temperature representative of themold surface (ts-Ta), which provides us a series of points that fit astraight line whose slope represents value α and the intersection of theline with the axis of the ordinates (axis ρ/μ) represents value m.

From a dimensional analysis, it is known that:

    Nu=(A(Cpu).sup.f /K) (ρDV)j/μ)=APr.sup.f Re.sup.j =C.sub.1 Re.sup.j

Where Nu is the Nusselt number, Pr is the Prandtl number and Re theReynolds number. If constant A and the Prandt approximate a constant C₁due to normal atmospheric conditions, the range of variations isnegligible.

Therefore, in this equation, factor j depends on the geometry of themold, nozzles, distance between them, etc.

To quantify j we measure the air flow and its static pressure and findthe value of n by an equation:

    Q=C×p.sup.n

Where Q is air flow, C is a constant that depends on the geometry of theducts, pressure drops, etc., P is the static air pressure in the ductand n is a factor that relates the air velocity to its static pressure.Therefore, if we graph static pressure P against Ta-(ts-Ta), a straightline is obtained whose slope defines the value of (1+J)/n and hence J isquantified and the intersection of said line with axis ts-Ta, gives avalue that corresponds to (log-β*-Jm)/(1+αj) and, since α, j and m areknown, it is possible to know β* which is the factor that is a functionof the operating conditions and geometry of the machine.

It is further concluded that high value of β* imply mainly highproduction rates, heavy articles or high glass temperature or acombination of them; these high values of β* require a better design ofthe nozzles (parameter j), less air leaks or losses by friction(parameter n), etc.

Then parameter β* will be a function of the manufacturing "history"mainly of the article and parameter j/n will refer to the design of themachine from the cooling viewpoint.

Tests run at the K-2 plant in Monterrey, N.L., MEXICO (I-S machines, 2sections, acticles 50 grams, 23 cuts per minute) proved the viability ofthis heat model.

Thus, this invention teaches how to achieve a heat model which relatesthe conditions of the cooling fluid with the data of operation, modes ofoperation, production and type of shaping machine. Such a heat modelmakes it possible to provide a cooling system which is absolutelyflexible and automatic so that cooling of the actual mold is madeindependent of variations of the ambient medium. On the basis of theheat model and keeping in mind the need of an automatic control, it ispossible to provide an electronic system for controlling cooling ofmolds. Accordingly by detecting the physical conditions of the coolingfluid such as temperature and humidity and its static pressure, atpredetermined intervals of time, it becomes possible--by a program thatcontains an equation as discussed above contained in the computer memoryand through other suitable means--to achieve an effective controlnecessary in cooling of the articles and/or molds, whereby the qualityof the articles produced and/or production of the shaping machines areimproved.

Although the system of this invention for cooling molds includes theheat model described above, it is possible to include other types ofheat models.

3. Having a forecasting model for predicting the changes in the physicalconditions of the ambient air and the pressure of the cooling air in theduct needed for said predicted conditions, by measuring said actualtemperature, humidity and pressure at predetermined intervals of time,for example each 2 hr. (at difference with Fertik's system which needsthe continuous monitoring thereof), for establishing the ambientbehavior history on which said forecasting is based and for correcting,if necessary, said parameters of the forecasting model which will beup-dated self-correcting the initial values gave to said model.

With this characteristic, the cooling system is independent of thetemperature, humidity and pressure detections because if one or more ofthe sensors fail, the system will be working permitting the personal tochange the defective sensors.

For said forecasting model, data measurements obtained in-line on aglass forming machine under a plant environment and consisting ofcooling air pressure Pat, ambient air temperature Tat, and the externalmold surface temperature T_(bt), were analyzed using discrete timeseries based on the Box Jenkins method. From the analysis, a dynamicmodel is given for predicting the values of the mold surface temperatureT_(bt). The accuracy of the forecast model is corraborated with actualdata. A control equation is derived for making the necessary adjustmentsof P_(at), and compensations for variations in T_(at), to ensure theregulation or minimum deviations, of the output T_(bt), from the targetset point.

The analyzed data were taken at discrete time intervals of 2 minutesunder normal operation conditions. The total sampling time being 9 hoursand the production container 12 OZ. at an I.S. double cavity machine (57bpm) located at our plant, VIQUESA, in Queretaro, Mexico.

Since T_(at) is an observable variable and not being able to bemanipulated, perturbations were induced in P_(at) in order to know thedynamic response of the system (T_(bt)).

A preliminary analysis of the raw data showed that T_(b).sbsb.t could bewell represented by an ARMA (p, q) model whose spectral density functionhad two well defined spikes at values of about 6 minutes and 2 hours.The first one being due to the proper opening-closing function and thesecond, not clearly identified, is believed to come probably from batchcharging operation, inherent viscosity variations, gob weight variationsor some action taken in the heating/cooling system during the stages ofmelting, refining or conditioning.

In order to get rid of the complex arma structure, the data was smoothedby taking averages (each 3 observations) and the generated new data wasused to build the dynamic model.

Using the smoothed data the identification and estimation stages weremade and conducted to several possible models. Among them three wereselected for further study since their residual sum of squares, noiseautocorrelation and transfer function weights showed that the data werewell represented by them.

Two of the models have the general form:

    T.sub.b.sbsb.t =F.sub.2 (B)P.sub.a.sbsb.t +F.sub.1 (B)T.sub.a.sbsb.t +N.sub.t                                                  ( 1)

Where:

T_(b).sbsb.t =is the deviation of T_(b).sbsb.t from its mean

F₂ (B) is a ratio of polynomials in the back order operator B andrepresents the transfer function due to P_(a).sbsb.t

F₁ (B) is the transfer fuction due to T_(a).sbsb.t and

N_(t) is the noise given by an ARMA (p, q) model.

The third model have the same basic structure as (1) but the variablesare expressed as deviations of their values at time t from those at timet-1, and the noise model having a MA (q) structure, however infactorizing this noise model in order to have deviations in N_(t), thedeviations will be cancelled and arrive to equation (1). The basicdifference among them is in the values of the transfer fuction and noisemodel parameters, which were estimated at the 95% confidence limits. Thecontrol equation has already been implemented in a microprocessor andits adequancy is being checked in-line, and is relatively easy toimplement in a microprocessor due to the linear structure of the model.

4. And the need to achieve a control capable of totally automatic butwith a manual operation capability, higly flexible in its operation andwith a high reliability index. It is easy to operate, with lowmaintenance, with monitoring of the process information, economy in theprocess and the other parameters inherent in these requirements.

BRIEF SUMMARY OF THE INVENTION

Therefore, the principal object of this invention is to provide anelectronic control system for cooling molds in glassware formingmachines, by which through monitoring continuously the velocity of themachine, the heat profile of the glass gob and the gob weight, it ispossible to determine the actual thermal excitation of the molds inorder that, if a variation of the thermal conditions of entrance to themolds appear, the cooling system could compensate the cooling needs forsaid variations.

Another principal object of this invention is to provide an electroniccontrol system for cooling molds in glassware forming machines, by whichthrough monitoring, at predetermined intervals of time, temperature andhumidity of the cooling air and its static pressure in the duct andrelating them with the manufacturing process conditions it is possibleto determine the physical properties of the cooling air and its coolingcapacity for said manufacturing process conditions in order tocompensate for said ambient variations making the system independent ofvariations of the ambient and to improve the quality of the productand/or production rate.

A further object of this invention is to provide an electronic controlsystem for cooling molds in glassware forming machines having aforecasting model for predicting through said measurements oftemperature and humidity of the cooling air and its pressure in theduct, at predetermined intervals of time, the changes in the ambientconditions and the pressure of the cooling air in the duct needed forsaid predicted conditions in order to establishing the ambient behaviorhistory on which said forecasting is based and correcting, if necessarythe parameters of the forecasting model wich will be up-datedself-correcting the initial values gave to said model.

Another further object of the invention is to provide an electronicsystem for cooling molds which is totally automatic and flexible yetprovides manual operation capability combined with high reliabilityindex, easy of operation, low maintenance, monitoring of processinformation and economy of operation.

These and other objects and advantages of the invention will be evidentto those skilled in this art form the following detailed description ofthe invention, when read in connection with the attached drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of the system of this invention forcooling of molds useful in the making of glass articles; and

FIG. 2 is a block diagram of the electronic mold cooling system.

DETAILED DESCRIPTION

With reference to the drawings, cooling of the molds M in machines forproducing articles of glass or other materials, such as the I-S machineswhich normally include eight sections, is achieved by feeding coolingair from the ambient medium by a fan 1 to a main duct 2 which connectswith a secondary duct 3, for supplying cooling air to cooling ducts 4which lead to the different sections of the machine.

Duct 3 is preferrably designed so that it is possible to absorb pressuredrops in the supply to the different sections of the machinesirrespective of the number of sections being operated at any given time.

Shutter valve 6 located in the duct 3, upstream of cooling ducts 4,regulates the mass flow of cooling air to the different sections of themachines through ducts 4.

The electronic control system for cooling of molds, according to thisinvention includes:

A gob cutting sensor 6 of any suitable type, which continuously detectsand supplies a signal representative of the velocity of the machine, agob temperature sensor 7, such as a fotodetector which continuouslydetect the temperature of the glass gob when said gob is passing intothe mold and supplies a signal representative of the heat profile of theglass gobs, and a gob weight sensor 8 which could be integrated to themachine or a bascule weighing the finished articles, which continuouslydetect and supplies a signal representative of the gob weight. Thesignals of the three sensors 6, 7 and 8 are fed through an indicatorpanel 9 to a microprocessor 10 having in its memory program an equationwhich relates said signals to determining the thermal excitation of themolds in order that, if a variation on the thermal condition of entranceto the mold appear, said microprocessor 10 will compensate the coolingneeds for said variations by moving the shutter valve 3 through anactuator 11 or alternatively by controlling the speed of the fan 1through said actuator 11.

A pressure sensor 12, of any suitable type, a temperature sensor 13 suchas a thermocouple and a humidity sensor 14, provide electrical analogsignals representative of the pressure, temperature and humidity of thecooling air in duct 3 to said microprocessor 10 each 2 hours or anotherpredetermined interval of time. Said microprocessor 10 includes in itsmemory program an equation which, through said detected pressure,temperature and humidity of the cooling air, calculates the physicalcondition of said cooling air and relates them with the data of themanufacturing process which includes the models of operation, productionand type of the forming machine, glass temperature, types of glass,production rate (cuts per minute), etc., fed to said microprocessor 10directly by the keyboard of said indicator panel 9 or by any suitableelement such as cards, discs, tapes, etc., in order to compensate forvariations in the ambient conditions and cooling capacity of saidcooling air.

Microprocessor 10 also includes a forecasting program which, based onthe history of the ambient behavior provided by sensors 12, 13 and 14,will correct, if necessary, the parameters of the forecasting programup-dating and self-correcting the initial values gave to the same andwill perit the cooling system to operate accurately even when saiddetectors 12, 13 and 14 fail, making the system practically independentfrom the sensors.

With reference to FIG. 2, gob cutting sensor 6, gob temperature sensor 7and gob weight sensor 8 continuously send a signal representing thevelocity of the machine, the thermal profile of the glass gob and itsweight to the microprocessor 10 through an analog-digital conversionmodule 15. In the same way, air pressure sensor 12, air temperaturesensor 13 and air humidity sensor 14 each 2 hours send a signalrepresentative of the pressure, temperature and humidity of the coolingair in the duct, through said analog-digital conversion module, so thatmicroprocessor 10, through its programs, carry out the necessaryadjustments and controls the entire cooling process by the actuation ofthe shutter valve 5 and/or alternatively controlling the speed of thefan, through a digital signal converted to analogous signal by a digitalto analogous conversion module, fed to actuator 11 for operate theshutter valve 5.

As previously stated, indicator panel 9 may include displays in order tocheck the values of the variables fed to microprocessor 10 and keyboardsfor feeding data needed by microprocessor 10.

The components of this electronic system can be selected from any knowntype.

Finally, it should be understood that the invention is not limitedexclusively to the design of the embodiment disclosed but experts in thefield will be enabled by the teaching of this invention to make changesin the design and distribution of its constitutent parts, while stillbeing clearly within the true spirit and scope of the invention setforth in the following claims.

I claim:
 1. In a glassware forming machine of the type includingmultiple sections each having multiple molds for receiving andprocessing glass gobs to produce glassware articles and having a moldcooling system which essentially comprises a source of cooling air, amanifold for said cooling air, a plurality of nozzles directing thecooling air to said molds, and flow control means for varying the flowrate of the cooling air through the manifold, the method for controllingthe cooling of said molds, comprising:sensing, through first sensormeans, the velocity of operation of the forming machine to derivesignals representative thereof; sensing, through second sensor means,the temperature and weight of the glass gobs fed to the molds of themachine, to derive signals representative thereof; sensing, throughthird sensor means, the temperature, humidity and pressure of thecooling air in the manifold of the machine, to derive signalsrepresentative thereof; supplying said signals provided by the first,second and third sensor means to a microprocessor operative to provide afirst table for processing the signals of the first and second sensormeans in order to determine the actual thermal excitation of the moldsand to derive command signals to control the flow rate of cooling air,and operative to provide a second table for processing the signals ofthe third sensor means in order to determine the physical conditions ofthe cooling air, and operative to provide a third table for recordingthe history of the operation conditions detected by all the sensor meansand forecast, through said history, the changes of weather conditions,with up-dating and self-correction of the initial values and commandsignals; feeding the command signals derived by the microprocessor fromsaid first and second tables to control means for controlling the rateof cooling air in accordance with the actual cooling needs of the molds;and, in the event of loss of any one of said first, second and thirdsignals, substituting for the lost signal a signal derived from saidhistorical memory of said third table.